For over a hundred years, public and academic medical universities and institutions, pathology clinics, private biomedical institutions, tissue archives, hospitals, and museums have been preserving biological specimens with formalin and other chemical fixatives such as formaldehyde and ethyl alcohol. The most common fixative is formalin. Formalin is used as a fixative because of it superior ability to preserve both tissue structure and cellular morphology. This has resulted in the wide use of formalin for the successful preservation of histologic sections for traditional microscopic analysis. Formalin fixation is so effective in preserving tissue structure and cellular morphology that the formalin archive is a veritable treasure trove containing millions of samples. Within this archive are biological samples of healthy tissue, tissue samples from virtually every known human disease, and a multitude of preserved life forms.
Formalin fixation occurs through the cross-linking of proteins within the biological specimen. These protein cross links, while providing excellent cellular morphology preservation, also renders the fixed sample relatively insoluble. Because of these protein cross-links, the types of assays that can be performed on a formalin-fixed sample are limited in number, unable to provide quantitative results and lack sensitivity. In fact, formalin fixed biological samples are virtually unusable in many modern assay techniques, which are both highly quantitative and sensitive.
Thus, there is an unmet need in the industry to use histologically processed samples to generate preparations from these samples that contain subsets of biomolecules contained in the samples, and to combine these subsets to generate a library containing the entirety of the biomolecular components of a given histopathologically processed biological sample.